As known, it is now common in bicycles to use disc brakes. Such brakes are indeed often preferred to other kinds of conventional brakes because they ensure a high braking force and they are less subject to problems caused by debris, such as mud or water.
Typically, a disc brake comprises a brake caliper fixed on the frame of the bicycle and a brake disc assembly comprising a brake disc mounted on a hub of a wheel. Inside the brake caliper there are two or four opposite brake pads. The brake disc rotates inside the space defined between the opposite pads. By actuating the brake lever, the pads are brought towards the brake disc, generating friction on the brake disc.
The coupling of the brake disc with the hub has the function of transferring the forces generated between the brake pads and the brake disc to the hub, so as to create a resistant torque on the hub of the wheel and obtain braking.
For this purpose, the brake disc is locked on the hub by bolts or by a shape fitting between the outer surface of the hub and the inner surface of a hole in the central portion of the brake disc.
In order to ensure that the brake disc is arranged between the space available between the pads of the brake caliper, the latter is provided with adjusters that allow an axial displacement of the caliper body with respect to the frame of the bicycle (and thus with respect to the brake disc).
In the case in which it is necessary to replace the wheel of the bicycle or to replace the brake disc, it is necessary to act on the adjusters of the brake caliper to ensure the centering of the brake disc between the pads.
Indeed, the machining tolerances and above all the clearances created in the mounting step of the brake disc on the hub are such that two nominally identical wheels have slight differences in the axial position of the brake disc with respect to a fixed reference (the frame of the bicycle).
Such slight differences in the axial position of the brake disc require action on the adjusters of the brake caliper to center the brake disc between the pads.
The Applicant has noted that the necessary adjustment of the adjusters of the brake caliper involves a time to change the wheel that is incompatible, for example, with the requirements of speed of wheel change during a cycling race.
The Applicant has further noted that the prolonged and continuous actuation of the adjusters of the brake caliper, especially if carried out by non-experts, can cause them to be damaged and consequently malfunction.
Document U.S. Pat. No. 9,267,560 B2 describes a bicycle brake disc assembly comprising a mechanism for adjusting the axial position of the brake disc with respect to the hub. The adjustment mechanism comprises an elastic element, such as a spring, active between the brake disc and the hub of the wheel. The brake disc is locked in a predetermined axial position by locking members, active on the hub and on the brake disc, counteracting the action of the elastic element. By selecting the axial position in which to activate the locking members it is possible to select the axial position of the brake disc.
The Applicant has perceived that it would be advantageous to have a simple and cost-effective brake disc assembly allowing a wheel change without having to intervene on the adjusters of the brake caliper.